Processing media data using a generic descriptor for file format boxes

ABSTRACT

In one example, a device for retrieving media data includes a memory configured to store media data, and a processor implemented in circuitry and configured to: process a descriptor of a manifest file of media content including the media data, the descriptor corresponding to an adaptation set of the media content and including data representative of a box of file level information that describes a property of a track of a media file of the media content including media data of the adaptation set, determine whether to retrieve the media data of the adaptation set according to the data representative of the file level information, and in response to determining to retrieve the media data, send a request to retrieve the media data.

This application claims the benefit of U.S. Provisional Application No. 62/530,761, filed Jul. 10, 2017, the entire contents of which are incorporated by reference.

TECHNICAL FIELD

This disclosure relates to storage and transport of encoded video data.

BACKGROUND

Digital video capabilities can be incorporated into a wide range of devices, including digital televisions, digital direct broadcast systems, wireless broadcast systems, personal digital assistants (PDAs), laptop or desktop computers, digital cameras, digital recording devices, digital media players, video gaming devices, video game consoles, cellular or satellite radio telephones, video teleconferencing devices, and the like. Digital video devices implement video compression techniques, such as those described in the standards defined by MPEG-2, MPEG-4, ITU-T H.263 or ITU-T H.264/MPEG-4, Part 10, Advanced Video Coding (AVC), ITU-T H.265 (also referred to High Efficiency Video Coding (HEVC)), and extensions of such standards, to transmit and receive digital video information more efficiently.

After video data has been encoded, the video data may be packetized for transmission or storage. The video data may be assembled into a video file conforming to any of a variety of standards, such as the International Organization for Standardization (ISO) base media file format and extensions thereof, such as AVC.

SUMMARY

In general, this disclosure describes various example designs for a generic descriptor for file format boxes, which can be used to conveniently expose file format level information into a media presentation description (MPD) of dynamic adaptive streaming over HTTP (DASH), session description protocol (SDP), and other such streaming protocols. The designs provide an automated descriptor generation from file format boxes to avoid complex definition later and also avoid mismatches. Although the ideas are described in the context of DASH and ISO base media file format, the mechanism applies to other media container file formats and other media delivery format and protocols.

In one example, a method of retrieving media data includes processing a descriptor of a manifest file of media content, the descriptor corresponding to an adaptation set of the media content and including data representative of a box of file level information that describes a property of a track of a media file of the media content including media data of the adaptation set, determining whether to retrieve the media data of the adaptation set according to the data representative of the file level information, and in response to determining to retrieve the media data, sending a request to retrieve the media data.

In another example, a device for retrieving media data includes a memory configured to store media data, and a processor implemented in circuitry and configured to process a descriptor of a manifest file of media content including the media data, the descriptor corresponding to an adaptation set of the media content and including data representative of a box of file level information that describes a property of a track of a media file of the media content including media data of the adaptation set, determine whether to retrieve the media data of the adaptation set according to the data representative of the file level information, and in response to determining to retrieve the media data, send a request to retrieve the media data.

In another example, a device for retrieving media data includes means for processing a descriptor of a manifest file of media content, the descriptor corresponding to an adaptation set of the media content and including data representative of a box of file level information that describes a property of a track of a media file of the media content including media data of the adaptation set, means for determining whether to retrieve the media data of the adaptation set according to the data representative of the file level information, and means for sending a request to retrieve the media data in response to determining to retrieve the media data.

In another example, a computer-readable storage medium has stored thereon instructions that, when executed, cause a processor to process a descriptor of a manifest file of media content, the descriptor corresponding to an adaptation set of the media content and including data representative of a box of file level information that describes a property of a track of a media file of the media content including media data of the adaptation set, determine whether to retrieve the media data of the adaptation set according to the data representative of the file level information, and send a request to retrieve the media data in response to determining to retrieve the media data.

In another example, a method of generating media data includes processing a box of file level information that describes a property of a track of a media file of media content including media data, generating a descriptor for a manifest file of the media content, the descriptor corresponding to an adaptation set of the media content and including data representative of the box of the file level information, the media data of the track being included in the adaptation set, and sending the manifest file including the descriptor to a client device.

In another example, a device for generating media data includes a memory configured to store media data, and a processor implemented in circuitry and configured to process a box of file level information that describes a property of a track of a media file of media content including the media data, generate a descriptor for a manifest file of the media content, the descriptor corresponding to an adaptation set of the media content and including data representative of the box of the file level information, the media data of the track being included in the adaptation set, and send the manifest file including the descriptor to a client device.

In another example, a device for generating media data includes means for processing a box of file level information that describes a property of a track of a media file of media content including media data, means for generating a descriptor for a manifest file of the media content, the descriptor corresponding to an adaptation set of the media content and including data representative of the box of the file level information, the media data of the track being included in the adaptation set, and means for sending the manifest file including the descriptor to a client device.

In another example, a computer-readable storage medium has stored thereon instructions that, when executed, cause a processor to process a box of file level information that describes a property of a track of a media file of media content including media data, generate a descriptor for a manifest file of the media content, the descriptor corresponding to an adaptation set of the media content and including data representative of the box of the file level information, the media data of the track being included in the adaptation set, and send the manifest file including the descriptor to a client device.

The details of one or more examples are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating an example system that implements techniques for streaming media data over a network.

FIG. 2 is a block diagram illustrating an example set of components of a retrieval unit.

FIG. 3 is a conceptual diagram illustrating elements of example multimedia content.

FIG. 4 is a block diagram illustrating elements of an example video file, which may correspond to a segment of a representation.

FIG. 5 is a conceptual diagram illustrating an example content model for DASH multitrack.

FIG. 6 is a conceptual diagram illustrating an example client model.

FIG. 7 is a flowchart illustrating an example method for generating media data and for retrieving media data in accordance with the techniques of this disclosure.

DETAILED DESCRIPTION

The techniques of this disclosure may be applied to video files conforming to video data encapsulated according to any of ISO base media file format (ISOBMFF), extensions to ISOBMFF, Scalable Video Coding (SVC) file format, Advanced Video Coding (AVC) file format, High Efficiency Video Coding (HEVC) file format, Third Generation Partnership Project (3GPP) file format, and/or Multiview Video Coding (MVC) file format, or other video file formats. A draft of ISO BMFF is specified in ISO/IEC 14496-12, available from phenix.int-evry.fr/mpeg/doc_end_user/documents/111_Geneva/wg11/w15177-v6-w15177.zip. A draft of another example file format, MPEG-4 file format, is specified in ISO/IEC 14496-15, available from wg11.sc29.org/doc_end_user/documents/115_Geneva/wg11/w16169-v2-w16169.zip.

ISOBMFF is used as the basis for many codec encapsulation formats, such as the AVC file format, as well as for many multimedia container formats, such as the MPEG-4 file format, the 3GPP file format (3GP), and the digital video broadcasting (DVB) file format.

In addition to continuous media, such as audio and video, static media, such as images, as well as metadata can be stored in a file conforming to ISOBMFF. Files structured according to the ISOBMFF may be used for many purposes, including local media file playback, progressive downloading of a remote file, segments for Dynamic Adaptive Streaming over HTTP (DASH), containers for content to be streamed and its packetization instructions, and recording of received real-time media streams.

A box is an elementary syntax structure in ISOBMFF, including a four-character coded box type, the byte count of the box, and the payload. An ISOBMFF file includes a sequence of boxes, and boxes may contain other boxes. According to ISOBMFF, a Movie box (“moov”) contains the metadata for the continuous media streams present in the file, each one represented in the file as a track. Per ISOBMFF, metadata for a track is enclosed in a Track box (“trak”), while the media content of a track is either enclosed in a Media Data box (“mdat”) or provided directly in a separate file. The media content for tracks includes a sequence of samples, such as audio or video access units.

ISOBMFF specifies the following types of tracks: a media track, which contains an elementary media stream, a hint track, which either includes media transmission instructions or represents a received packet stream, and a timed metadata track, which comprises time-synchronized metadata.

Although originally designed for storage, the ISOBMFF has proven to be very valuable for streaming, e.g., for progressive download or DASH. For streaming purposes, movie fragments defined in ISOBMFF can be used.

The metadata for each track includes a list of sample description entries, each providing the coding or encapsulation format used in the track and the initialization data needed for processing that format. Each sample is associated with one of the sample description entries of the track.

The ISOBMFF enables specifying sample-specific metadata with various mechanisms. Specific boxes within the Sample Table box (“stbl”) have been standardized to respond to common needs. For example, a Sync Sample box (“stss”) is used to list the random access samples of the track. The sample grouping mechanism enables mapping of samples according to a four-character grouping type into groups of samples sharing the same property specified as a sample group description entry in the file. Several grouping types have been specified in the ISOBMFF.

Virtual reality (VR) is the ability to be virtually present in a virtual, non-physical world created by the rendering of natural and/or synthetic images and sounds correlated by movements of an immersed user, allowing interaction with that virtual world. With recent progress made in rendering devices, such as head mounted displays (HMD) and VR video (often also referred to as 360-degree video) creation, a significant quality of experience can be offered. VR applications include gaming, training, education, sports video, online shopping, entrainment, and so on.

A typical VR system includes the following components and steps:

-   -   1) A camera set, which typically includes multiple individual         cameras pointing in different directions, ideally collectively         covering all viewpoints around the camera set.     -   2) Image stitching, where video pictures taken by the multiple         individual cameras are synchronized in the time domain and         stitched in the space domain, to be a spherical video, but         mapped to a rectangular format, such as equi-rectangular (like a         world map) or cube map.     -   3) The video in the mapped rectangular format is         encoded/compressed using a video codec, e.g., H.265/HEVC or         H.264/AVC.     -   4) The compressed video bitstream(s) may be stored and/or         encapsulated in a media format and transmitted (possibly only         the subset covering the area being seen by a user, sometimes         referred to as the viewport) through a network to a receiving         device (e.g., a client device).     -   5) The receiving device receives the video bitstream(s) or part         thereof, possibly encapsulated in a file format, and sends the         decoded video signal or part thereof to a rendering device         (which may be included in the same client device as the         receiving device).     -   6) The rendering device can be, e.g., an HMD, which can track         head movement and even eye move moment, and may render the         corresponding part of the video such that an immersive         experience is delivered to the user.

Omnidirectional MediA Format (OMAF) is being developed by the Moving Pictures Experts Group (MPEG) to define a media format that enables omnidirectional media applications, focusing on VR applications with 360-degree video and associated audio. OMAF specifies a list of projection methods that can be used for conversion of a spherical or 360-degree video into a two-dimensional rectangular video, followed by how to store omnidirectional media and the associated metadata using the ISO base media file format (ISOBMFF) and how to encapsulate, signal, and stream omnidirectional media using dynamic adaptive streaming over HTTP (DASH), and finally, which video and audio codecs, as well as media coding configurations, can be used for compression and playback of the omnidirectional media signal. OMAF is to become ISO/IEC 23090-2, and a draft specification is available from wg11.sc29.org/doc_end_user/documents/119_Torino/wg11/m40849-v1-m40849_OMAF_text_Berlin_output.zip.

In HTTP streaming protocols, such as DASH, frequently used operations include HEAD, GET, and partial GET. The HEAD operation retrieves a header of a file associated with a given uniform resource locator (URL) or uniform resource name (URN), without retrieving a payload associated with the URL or URN. The GET operation retrieves a whole file associated with a given URL or URN. The partial GET operation receives a byte range as an input parameter and retrieves a continuous number of bytes of a file, where the number of bytes correspond to the received byte range. Thus, movie fragments may be provided for HTTP streaming, because a partial GET operation can get one or more individual movie fragments. In a movie fragment, there can be several track fragments of different tracks. In HTTP streaming, a media presentation may be a structured collection of data that is accessible to the client. The client may request and download media data information to present a streaming service to a user.

DASH is specified in ISO/IEC 23009-1, and is a standard for HTTP (adaptive) streaming applications. ISO/IEC 23009-1 mainly specifies the format of the media presentation description (MPD), also known as a manifest or manifest file, and media segment formats. The MPD describes the media available on a server and allows a DASH client to autonomously download an appropriate media version at an appropriate media time.

In the example of streaming 3GPP data using HTTP streaming, there may be multiple representations for video and/or audio data of multimedia content. As explained below, different representations may correspond to different coding characteristics (e.g., different profiles or levels of a video coding standard), different coding standards or extensions of coding standards (such as multiview and/or scalable extensions), or different bitrates. The manifest of such representations may be defined in a Media Presentation Description (MPD) data structure. A media presentation may correspond to a structured collection of data that is accessible to an HTTP streaming client device. The HTTP streaming client device may request and download media data information to present a streaming service to a user of the client device. A media presentation may be described in the MPD data structure, which may include updates of the MPD.

A media presentation may contain a sequence of one or more Periods. Each period may extend until the start of the next Period, or until the end of the media presentation, in the case of the last period. Each period may contain one or more representations for the same media content. A representation may be one of a number of alternative encoded versions of audio, video, timed text, or other such data. The representations may differ by encoding types, e.g., by bitrate, resolution, and/or codec for video data and bitrate, language, and/or codec for audio data. The term representation may be used to refer to a section of encoded audio or video data corresponding to a particular period of the multimedia content and encoded in a particular way.

Representations of a particular period may be assigned to a group indicated by an attribute in the MPD indicative of an adaptation set to which the representations belong. Representations in the same adaptation set are generally considered alternatives to each other, in that a client device can dynamically and seamlessly switch between these representations, e.g., to perform bandwidth adaptation. For example, each representation of video data for a particular period may be assigned to the same adaptation set, such that any of the representations may be selected for decoding to present media data, such as video data or audio data, of the multimedia content for the corresponding period. The media content within one period may be represented by either one representation from group 0, if present, or the combination of at most one representation from each non-zero group, in some examples. Timing data for each representation of a period may be expressed relative to the start time of the period.

A representation may include one or more segments. Each representation may include an initialization segment, or each segment of a representation may be self-initializing. When present, the initialization segment may contain initialization information for accessing the representation. In general, the initialization segment does not contain media data. A segment may be uniquely referenced by an identifier, such as a uniform resource locator (URL), uniform resource name (URN), or uniform resource identifier (URI). The MPD may provide the identifiers for each segment. In some examples, the MPD may also provide byte ranges in the form of a range attribute, which may correspond to the data for a segment within a file accessible by the URL, URN, or URI.

Different representations may be selected for substantially simultaneous retrieval for different types of media data. For example, a client device may select an audio representation, a video representation, and a timed text representation from which to retrieve segments. In some examples, the client device may select particular adaptation sets for performing bandwidth adaptation. That is, the client device may select an adaptation set including video representations, an adaptation set including audio representations, and/or an adaptation set including timed text. Alternatively, the client device may select adaptation sets for certain types of media (e.g., video), and directly select representations for other types of media (e.g., audio and/or timed text).

A typical procedure for DASH based HTTP streaming includes the following steps:

-   -   1) A DASH client obtains the MPD of a streaming content, e.g., a         movie. The MPD includes information on different alternative         representations, e.g., bit rate, video resolution, frame rate,         audio language, of the streaming content, as well as URLs of the         HTTP resources (the initialization segment and the media         segments).     -   2) Based on information in the MPD and local information         available to the DASH client, e.g., network bandwidth,         decoding/display capabilities, and user preferences, the DASH         client requests the desired representation(s), one segment (or a         part thereof) at a time.     -   3) When the DASH client detects a network bandwidth change, it         requests segments of a different representation with a         better-matching bitrate, ideally starting from a segment that         starts with a random access point.

During an HTTP streaming “session,” to respond to a user request to seek backward to a past position or forward to a future position, the DASH client requests past or future segments starting from a segment that is close to the desired position and that ideally starts with a random access point. The user may also request to fast-forward the content, which may be realized by requesting data sufficient for decoding only intra-coded video pictures or only a temporal subset of the video stream.

Video data may be encoded according to a variety of video coding standards. Such video coding standards include ITU-T H.261, ISO/IEC MPEG-1 Visual, ITU-T H.262 or ISO/IEC MPEG-2 Visual, ITU-T H.263, ISO/IEC MPEG-4 Visual, ITU-T H.264 or ISO/IEC MPEG-4 AVC, including its Scalable Video Coding (SVC) and Multiview Video Coding (MVC) extensions, and High-Efficiency Video Coding (HEVC), also known as ITU-T H.265 and ISO/IEC 23008-2, including its scalable coding extension (i.e., scalable high-efficiency video coding, SHVC) and multiview extension (i.e., multiview high efficiency video coding, MV-HEVC).

The OMAF draft specification describes various DASH descriptors for OMAF. Clause 8.2.1 of the OMAF draft specification specifies the projection format (PF) descriptor. Clause 8.2.2 of the OMAF draft specification specifies the region-wise packing (RWPK) descriptor. Clause 8.2.3 of the OMAF draft specification specifies the content coverage (CC) descriptor. Clause 8.2.4 of the OMAF draft specification specifies the region-wise quality ranking (RWQR) descriptor.

FIG. 1 is a block diagram illustrating an example system 10 that implements techniques for streaming media data over a network. In this example, system 10 includes content preparation device 20, server device 60, and client device 40. Client device 40 and server device 60 are communicatively coupled by network 74, which may comprise the Internet. In some examples, content preparation device 20 and server device 60 may also be coupled by network 74 or another network, or may be directly communicatively coupled. In some examples, content preparation device 20 and server device 60 may comprise the same device.

Content preparation device 20, in the example of FIG. 1 , comprises audio source 22 and video source 24. Audio source 22 may comprise, for example, a microphone that produces electrical signals representative of captured audio data to be encoded by audio encoder 26. Alternatively, audio source 22 may comprise a storage medium storing previously recorded audio data, an audio data generator such as a computerized synthesizer, or any other source of audio data. Video source 24 may comprise a video camera that produces video data to be encoded by video encoder 28, a storage medium encoded with previously recorded video data, a video data generation unit such as a computer graphics source, or any other source of video data. Content preparation device 20 is not necessarily communicatively coupled to server device 60 in all examples, but may store multimedia content to a separate medium that is read by server device 60.

Raw audio and video data may comprise analog or digital data. Analog data may be digitized before being encoded by audio encoder 26 and/or video encoder 28. Audio source 22 may obtain audio data from a speaking participant while the speaking participant is speaking, and video source 24 may simultaneously obtain video data of the speaking participant. In other examples, audio source 22 may comprise a computer-readable storage medium comprising stored audio data, and video source 24 may comprise a computer-readable storage medium comprising stored video data. In this manner, the techniques described in this disclosure may be applied to live, streaming, real-time audio and video data or to archived, pre-recorded audio and video data.

Audio frames that correspond to video frames are generally audio frames containing audio data that was captured (or generated) by audio source 22 contemporaneously with video data captured (or generated) by video source 24 that is contained within the video frames. For example, while a speaking participant generally produces audio data by speaking, audio source 22 captures the audio data, and video source 24 captures video data of the speaking participant at the same time, that is, while audio source 22 is capturing the audio data. Hence, an audio frame may temporally correspond to one or more particular video frames. Accordingly, an audio frame corresponding to a video frame generally corresponds to a situation in which audio data and video data were captured at the same time and for which an audio frame and a video frame comprise, respectively, the audio data and the video data that was captured at the same time.

In some examples, audio encoder 26 may encode a timestamp in each encoded audio frame that represents a time at which the audio data for the encoded audio frame was recorded, and similarly, video encoder 28 may encode a timestamp in each encoded video frame that represents a time at which the video data for encoded video frame was recorded. In such examples, an audio frame corresponding to a video frame may comprise an audio frame comprising a timestamp and a video frame comprising the same timestamp. Content preparation device 20 may include an internal clock from which audio encoder 26 and/or video encoder 28 may generate the timestamps, or that audio source 22 and video source 24 may use to associate audio and video data, respectively, with a timestamp.

In some examples, audio source 22 may send data to audio encoder 26 corresponding to a time at which audio data was recorded, and video source 24 may send data to video encoder 28 corresponding to a time at which video data was recorded. In some examples, audio encoder 26 may encode a sequence identifier in encoded audio data to indicate a relative temporal ordering of encoded audio data but without necessarily indicating an absolute time at which the audio data was recorded, and similarly, video encoder 28 may also use sequence identifiers to indicate a relative temporal ordering of encoded video data. Similarly, in some examples, a sequence identifier may be mapped or otherwise correlated with a timestamp.

Audio encoder 26 generally produces a stream of encoded audio data, while video encoder 28 produces a stream of encoded video data. Each individual stream of data (whether audio or video) may be referred to as an elementary stream. An elementary stream is a single, digitally coded (possibly compressed) component of a representation. For example, the coded video or audio part of the representation can be an elementary stream. An elementary stream may be converted into a packetized elementary stream (PES) before being encapsulated within a video file. Within the same representation, a stream ID may be used to distinguish the PES-packets belonging to one elementary stream from the other. The basic unit of data of an elementary stream is a packetized elementary stream (PES) packet. Thus, coded video data generally corresponds to elementary video streams. Similarly, audio data corresponds to one or more respective elementary streams.

Many video coding standards, such as ITU-T H.264/AVC and the upcoming High Efficiency Video Coding (HEVC) standard, define the syntax, semantics, and decoding process for error-free bitstreams, any of which conform to a certain profile or level. Video coding standards typically do not specify the encoder, but the encoder is tasked with guaranteeing that the generated bitstreams are standard-compliant for a decoder. In the context of video coding standards, a “profile” corresponds to a subset of algorithms, features, or tools and constraints that apply to them. As defined by the H.264 standard, for example, a “profile” is a subset of the entire bitstream syntax that is specified by the H.264 standard. A “level” corresponds to the limitations of the decoder resource consumption, such as, for example, decoder memory and computation, which are related to the resolution of the pictures, bit rate, and block processing rate. A profile may be signaled with a profile_idc (profile indicator) value, while a level may be signaled with a level_idc (level indicator) value.

The H.264 standard, for example, recognizes that, within the bounds imposed by the syntax of a given profile, it is still possible to require a large variation in the performance of encoders and decoders depending upon the values taken by syntax elements in the bitstream such as the specified size of the decoded pictures. The H.264 standard further recognizes that, in many applications, it is neither practical nor economical to implement a decoder capable of dealing with all hypothetical uses of the syntax within a particular profile. Accordingly, the H.264 standard defines a “level” as a specified set of constraints imposed on values of the syntax elements in the bitstream. These constraints may be simple limits on values. Alternatively, these constraints may take the form of constraints on arithmetic combinations of values (e.g., picture width multiplied by picture height multiplied by number of pictures decoded per second). The H.264 standard further provides that individual implementations may support a different level for each supported profile.

A decoder conforming to a profile ordinarily supports all the features defined in the profile. For example, as a coding feature, B-picture coding is not supported in the baseline profile of H.264/AVC but is supported in other profiles of H.264/AVC. A decoder conforming to a level should be capable of decoding any bitstream that does not require resources beyond the limitations defined in the level. Definitions of profiles and levels may be helpful for interpretability. For example, during video transmission, a pair of profile and level definitions may be negotiated and agreed for a whole transmission session. More specifically, in H.264/AVC, a level may define limitations on the number of macroblocks that need to be processed, decoded picture buffer (DPB) size, coded picture buffer (CPB) size, vertical motion vector range, maximum number of motion vectors per two consecutive MBs, and whether a B-block can have sub-macroblock partitions less than 8×8 pixels. In this manner, a decoder may determine whether the decoder is capable of properly decoding the bitstream.

In the example of FIG. 1 , encapsulation unit 30 of content preparation device 20 receives elementary streams comprising coded video data from video encoder 28 and elementary streams comprising coded audio data from audio encoder 26. In some examples, video encoder 28 and audio encoder 26 may each include packetizers for forming PES packets from encoded data. In other examples, video encoder 28 and audio encoder 26 may each interface with respective packetizers for forming PES packets from encoded data. In still other examples, encapsulation unit 30 may include packetizers for forming PES packets from encoded audio and video data.

Video encoder 28 may encode video data of multimedia content in a variety of ways, to produce different representations of the multimedia content at various bitrates and with various characteristics, such as pixel resolutions, frame rates, conformance to various coding standards, conformance to various profiles and/or levels of profiles for various coding standards, representations having one or multiple views (e.g., for two-dimensional or three-dimensional playback), or other such characteristics. A representation, as used in this disclosure, may comprise one of audio data, video data, text data (e.g., for closed captions), or other such data. The representation may include an elementary stream, such as an audio elementary stream or a video elementary stream. Each PES packet may include a stream_id that identifies the elementary stream to which the PES packet belongs. Encapsulation unit 30 is responsible for assembling elementary streams into video files (e.g., segments) of various representations.

Encapsulation unit 30 receives PES packets for elementary streams of a representation from audio encoder 26 and video encoder 28 and forms corresponding network abstraction layer (NAL) units from the PES packets. Coded video segments may be organized into NAL units, which provide a “network-friendly” video representation addressing applications such as video telephony, storage, broadcast, or streaming. NAL units can be categorized to Video Coding Layer (VCL) NAL units and non-VCL NAL units. VCL units may contain the core compression engine and may include block, macroblock, and/or slice level data. Other NAL units may be non-VCL NAL units. In some examples, a coded picture in one time instance, normally presented as a primary coded picture, may be contained in an access unit, which may include one or more NAL units.

Non-VCL NAL units may include parameter set NAL units and SEI NAL units, among others. Parameter sets may contain sequence-level header information (in sequence parameter sets (SPS)) and the infrequently changing picture-level header information (in picture parameter sets (PPS)). With parameter sets (e.g., PPS and SPS), infrequently changing information need not to be repeated for each sequence or picture, hence coding efficiency may be improved. Furthermore, the use of parameter sets may enable out-of-band transmission of the important header information, avoiding the need for redundant transmissions for error resilience. In out-of-band transmission examples, parameter set NAL units may be transmitted on a different channel than other NAL units, such as SEI NAL units.

Supplemental Enhancement Information (SEI) may contain information that is not necessary for decoding the coded pictures samples from VCL NAL units, but may assist in processes related to decoding, display, error resilience, and other purposes. SEI messages may be contained in non-VCL NAL units. SEI messages are the normative part of some standard specifications, and thus are not always mandatory for standard compliant decoder implementation. SEI messages may be sequence level SEI messages or picture level SEI messages. Some sequence level information may be contained in SEI messages, such as scalability information SEI messages in the example of SVC and view scalability information SEI messages in MVC. These example SEI messages may convey information on, e.g., extraction of operation points and characteristics of the operation points. In addition, encapsulation unit 30 may form a manifest file, such as a media presentation descriptor (MPD) that describes characteristics of the representations. Encapsulation unit 30 may format the MPD according to extensible markup language (XML).

Encapsulation unit 30 may provide data for one or more representations of multimedia content, along with the manifest file (e.g., the MPD) to output interface 32. Output interface 32 may comprise a network interface or an interface for writing to a storage medium, such as a universal serial bus (USB) interface, a CD or DVD writer or burner, an interface to magnetic or flash storage media, or other interfaces for storing or transmitting media data. Encapsulation unit 30 may provide data of each of the representations of multimedia content to output interface 32, which may send the data to server device 60 via network transmission or storage media. In the example of FIG. 1 , server device 60 includes storage medium 62 that stores various multimedia contents 64, each including a respective manifest file 66 and one or more representations 68A-68N (representations 68). In some examples, output interface 32 may also send data directly to network 74.

In some examples, representations 68 may be separated into adaptation sets. That is, various subsets of representations 68 may include respective common sets of characteristics, such as codec, profile and level, resolution, number of views, file format for segments, text type information that may identify a language or other characteristics of text to be displayed with the representation and/or audio data to be decoded and presented, e.g., by speakers, camera angle information that may describe a camera angle or real-world camera perspective of a scene for representations in the adaptation set, rating information that describes content suitability for particular audiences, or the like.

Manifest file 66 may include data indicative of the subsets of representations 68 corresponding to particular adaptation sets, as well as common characteristics for the adaptation sets. Manifest file 66 may also include data representative of individual characteristics, such as bitrates, for individual representations of adaptation sets. In this manner, an adaptation set may provide for simplified network bandwidth adaptation. Representations in an adaptation set may be indicated using child elements of an adaptation set element of manifest file 66.

Server device 60 includes request processing unit 70 and network interface 72. In some examples, server device 60 may include a plurality of network interfaces. Furthermore, any or all of the features of server device 60 may be implemented on other devices of a content delivery network, such as routers, bridges, proxy devices, switches, or other devices. In some examples, intermediate devices of a content delivery network may cache data of multimedia content 64, and include components that conform substantially to those of server device 60. In general, network interface 72 is configured to send and receive data via network 74.

Request processing unit 70 is configured to receive network requests from client devices, such as client device 40, for data of storage medium 62. For example, request processing unit 70 may implement hypertext transfer protocol (HTTP) version 1.1, as described in RFC 2616, “Hypertext Transfer Protocol—HTTP/1.1,” by R. Fielding et al, Network Working Group, IETF, June 1999. That is, request processing unit 70 may be configured to receive HTTP GET or partial GET requests and provide data of multimedia content 64 in response to the requests. The requests may specify a segment of one of representations 68, e.g., using a URL of the segment. In some examples, the requests may also specify one or more byte ranges of the segment, thus comprising partial GET requests. Request processing unit 70 may further be configured to service HTTP HEAD requests to provide header data of a segment of one of representations 68. In any case, request processing unit 70 may be configured to process the requests to provide requested data to a requesting device, such as client device 40.

Additionally or alternatively, request processing unit 70 may be configured to deliver media data via a broadcast or multicast protocol, such as eMBMS. Content preparation device 20 may create DASH segments and/or sub-segments in substantially the same way as described, but server device 60 may deliver these segments or sub-segments using eMBMS or another broadcast or multicast network transport protocol. For example, request processing unit 70 may be configured to receive a multicast group join request from client device 40. That is, server device 60 may advertise an Internet protocol (IP) address associated with a multicast group to client devices, including client device 40, associated with particular media content (e.g., a broadcast of a live event). Client device 40, in turn, may submit a request to join the multicast group. This request may be propagated throughout network 74, e.g., routers making up network 74, such that the routers are caused to direct traffic destined for the IP address associated with the multicast group to subscribing client devices, such as client device 40.

As illustrated in the example of FIG. 1 , multimedia content 64 includes manifest file 66, which may correspond to a media presentation description (MPD). Manifest file 66 may contain descriptions of different alternative representations 68 (e.g., video services with different qualities) and the description may include, e.g., codec information, a profile value, a level value, a bitrate, and other descriptive characteristics of representations 68. Client device 40 may retrieve the MPD of a media presentation to determine how to access segments of representations 68.

In particular, retrieval unit 52 may retrieve configuration data (not shown) of client device 40 to determine decoding capabilities of video decoder 48 and rendering capabilities of video output 44. The configuration data may also include any or all of a language preference selected by a user of client device 40, one or more camera perspectives corresponding to depth preferences set by the user of client device 40, and/or a rating preference selected by the user of client device 40. Retrieval unit 52 may comprise, for example, a web browser or a media client configured to submit HTTP GET and partial GET requests. Retrieval unit 52 may correspond to software instructions executed by one or more processors or processing units (not shown) of client device 40. In some examples, all or portions of the functionality described with respect to retrieval unit 52 may be implemented in hardware, or a combination of hardware, software, and/or firmware, where requisite hardware may be provided to execute instructions for software or firmware.

Retrieval unit 52 may compare the decoding and rendering capabilities of client device 40 to characteristics of representations 68 indicated by information of manifest file 66. Retrieval unit 52 may initially retrieve at least a portion of manifest file 66 to determine characteristics of representations 68. For example, retrieval unit 52 may request a portion of manifest file 66 that describes characteristics of one or more adaptation sets. Retrieval unit 52 may select a subset of representations 68 (e.g., an adaptation set) having characteristics that can be satisfied by the coding and rendering capabilities of client device 40. Retrieval unit 52 may then determine bitrates for representations in the adaptation set, determine a currently available amount of network bandwidth, and retrieve segments from one of the representations having a bitrate that can be satisfied by the network bandwidth.

In general, higher bitrate representations may yield higher quality video playback, while lower bitrate representations may provide sufficient quality video playback when available network bandwidth decreases. Accordingly, when available network bandwidth is relatively high, retrieval unit 52 may retrieve data from relatively high bitrate representations, whereas when available network bandwidth is low, retrieval unit 52 may retrieve data from relatively low bitrate representations. In this manner, client device 40 may stream multimedia data over network 74 while also adapting to changing network bandwidth availability of network 74.

Additionally or alternatively, retrieval unit 52 may be configured to receive data in accordance with a broadcast or multicast network protocol, such as eMBMS or IP multicast. In such examples, retrieval unit 52 may submit a request to join a multicast network group associated with particular media content. After joining the multicast group, retrieval unit 52 may receive data of the multicast group without further requests issued to server device 60 or content preparation device 20. Retrieval unit 52 may submit a request to leave the multicast group when data of the multicast group is no longer needed, e.g., to stop playback or to change channels to a different multicast group.

Network interface 54 may receive and provide data of segments of a selected representation to retrieval unit 52, which may in turn provide the segments to decapsulation unit 50. Decapsulation unit 50 may decapsulate elements of a video file into constituent PES streams, depacketize the PES streams to retrieve encoded data, and send the encoded data to either audio decoder 46 or video decoder 48, depending on whether the encoded data is part of an audio or video stream, e.g., as indicated by PES packet headers of the stream. Audio decoder 46 decodes encoded audio data and sends the decoded audio data to audio output 42, while video decoder 48 decodes encoded video data and sends the decoded video data, which may include a plurality of views of a stream, to video output 44.

Video encoder 28, video decoder 48, audio encoder 26, audio decoder 46, encapsulation unit 30, retrieval unit 52, and decapsulation unit 50 each may be implemented as any of a variety of suitable processing circuitry, as applicable, such as one or more microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), discrete logic circuitry, software, hardware, firmware or any combinations thereof. Each of video encoder 28 and video decoder 48 may be included in one or more encoders or decoders, either of which may be integrated as part of a combined video encoder/decoder (CODEC). Likewise, each of audio encoder 26 and audio decoder 46 may be included in one or more encoders or decoders, either of which may be integrated as part of a combined CODEC. An apparatus including video encoder 28, video decoder 48, audio encoder 26, audio decoder 46, encapsulation unit 30, retrieval unit 52, and/or decapsulation unit 50 may comprise an integrated circuit, a microprocessor, and/or a wireless communication device, such as a cellular telephone.

Client device 40, server device 60, and/or content preparation device 20 may be configured to operate in accordance with the techniques of this disclosure. For purposes of example, this disclosure describes these techniques with respect to client device 40 and server device 60. However, it should be understood that content preparation device 20 may be configured to perform these techniques, instead of (or in addition to) server device 60.

Encapsulation unit 30 may form NAL units comprising a header that identifies a program to which the NAL unit belongs, as well as a payload, e.g., audio data, video data, or data that describes the transport or program stream to which the NAL unit corresponds. For example, in H.264/AVC, a NAL unit includes a 1-byte header and a payload of varying size. A NAL unit including video data in its payload may comprise various granularity levels of video data. For example, a NAL unit may comprise a block of video data, a plurality of blocks, a slice of video data, or an entire picture of video data. Encapsulation unit 30 may receive encoded video data from video encoder 28 in the form of PES packets of elementary streams. Encapsulation unit 30 may associate each elementary stream with a corresponding program.

Encapsulation unit 30 may also assemble access units from a plurality of NAL units. In general, an access unit may comprise one or more NAL units for representing a frame of video data, as well audio data corresponding to the frame when such audio data is available. An access unit generally includes all NAL units for one output time instance, e.g., all audio and video data for one time instance. For example, if each view has a frame rate of 20 frames per second (fps), then each time instance may correspond to a time interval of 0.05 seconds. During this time interval, the specific frames for all views of the same access unit (the same time instance) may be rendered simultaneously. In one example, an access unit may comprise a coded picture in one time instance, which may be presented as a primary coded picture.

Accordingly, an access unit may comprise all audio and video frames of a common temporal instance, e.g., all views corresponding to time X. This disclosure also refers to an encoded picture of a particular view as a “view component.” That is, a view component may comprise an encoded picture (or frame) for a particular view at a particular time. Accordingly, an access unit may be defined as comprising all view components of a common temporal instance. The decoding order of access units need not necessarily be the same as the output or display order.

A media presentation may include a media presentation description (MPD), which may contain descriptions of different alternative representations (e.g., video services with different qualities) and the description may include, e.g., codec information, a profile value, and a level value. An MPD is one example of a manifest file, such as manifest file 66. Client device 40 may retrieve the MPD of a media presentation to determine how to access movie fragments of various presentations. Movie fragments may be located in movie fragment boxes (moof boxes) of video files.

Manifest file 66 (which may comprise, for example, an MPD) may advertise availability of segments of representations 68. That is, the MPD may include information indicating the wall-clock time at which a first segment of one of representations 68 becomes available, as well as information indicating the durations of segments within representations 68. In this manner, retrieval unit 52 of client device 40 may determine when each segment is available, based on the starting time as well as the durations of the segments preceding a particular segment.

After encapsulation unit 30 has assembled NAL units and/or access units into a video file based on received data, encapsulation unit 30 passes the video file to output interface 32 for output. In some examples, encapsulation unit 30 may store the video file locally or send the video file to a remote server via output interface 32, rather than sending the video file directly to client device 40. Output interface 32 may comprise, for example, a transmitter, a transceiver, a device for writing data to a computer-readable medium such as, for example, an optical drive, a magnetic media drive (e.g., floppy drive), a universal serial bus (USB) port, a network interface, or other output interface. Output interface 32 outputs the video file to a computer-readable medium, such as, for example, a transmission signal, a magnetic medium, an optical medium, a memory, a flash drive, or other computer-readable medium.

Network interface 54 may receive a NAL unit or access unit via network 74 and provide the NAL unit or access unit to decapsulation unit 50, via retrieval unit 52. Decapsulation unit 50 may decapsulate elements of a video file into constituent PES streams, depacketize the PES streams to retrieve encoded data, and send the encoded data to either audio decoder 46 or video decoder 48, depending on whether the encoded data is part of an audio or video stream, e.g., as indicated by PES packet headers of the stream. Audio decoder 46 decodes encoded audio data and sends the decoded audio data to audio output 42, while video decoder 48 decodes encoded video data and sends the decoded video data, which may include a plurality of views of a stream, to video output 44.

In accordance with the techniques of this disclosure, content preparation device 20 (or server device 60) may construct data for manifest file 66 (e.g., a DASH MPD) representative of file level information of a track of a media file, such as a track of a segment of one of representations 68. The data representative of the file level information may represent data of a box of the media file. The data may represent, for example, a four character code (4CC) of the box (also referred to as a code point), a version number of the box, and content of the box. The data may represent all of the data of the box or only a relevant portion of the box.

In some examples, encapsulation unit 30 of content preparation device 20 may automatically generate a descriptor of manifest file 66 from data of the box of the media file. Such descriptor may be an essential descriptor (e.g., if the track includes data other than a main media component) or a supplemental descriptor (e.g., if the track includes the main media component). Encapsulation unit 30 may generate a prefix such as “urn:mpeg:isobmff-dash:<4cc>:<version>,” preceding a value. The value of <4cc> may represent the four character code of the box, the value of <version> may represent the version of the box, and the following value may include data of the box itself, that is, all or a relevant portion of content of the box.

In this example, retrieval unit 52 may determine how to parse the value following the prefix based on the values of <4cc> and <version>. Retrieval unit 52 may then determine properties of the track using the descriptor, in particular, the content of the box represented in the value following the prefix. Retrieval unit 52 may further determine whether to select the track (and in particular, one of representations 68 or an adaptation set including one or more of representations 68 corresponding to one or more tracks including the track) based on the value following the prefix. For example, retrieval unit 52 may determine whether client device 40 is capable of decoding and rendering media data of the track, prioritize representations 68 (and tracks thereof), receive user input representing user preferences and select from among available representations 68 (and tracks thereof), or other such selection actions according to the value following the prefix.

Additionally or alternatively, encapsulation unit 30 may construct an element of manifest file 66 that can be used as an extension namespace in manifest file 66. Encapsulation unit 30 may generate the element such that all relevant parameters of the box can be document in an XML descriptor. For example, encapsulation unit 30 may use elements, attributes, mandatory and optional parameters, proper data types, or the like. Retrieval unit 52 may use the element and the extension namespace in a manner similar to the descriptor as discussed above, e.g., to select a track (and corresponding one of representations 68 or an adaptation set including one or more representations 68).

As yet another example, encapsulation unit 30 may automatically generate a descriptor as discussed above, but follow an automated syntax for expressing all data in the box, instead of a single value field. Encapsulation unit 30 may automatically generate XML or Augmented Backus-Naur Form (ABNF) formatted data for the descriptor. As an example, encapsulation unit 30 may construct a descriptor comprising a prefix “urn:mpeg:isobmff-dash:processing,” preceding a value, where the value defines an extension namespace identifier. Retrieval unit 52 may use the descriptor in a manner similar to the descriptor or element as discussed above, e.g., to select a track (and corresponding one of representations 68 or an adaptation set including one or more representations 68).

In this manner, content preparation device 20 and/or server device 60 represent examples of a device for generating media data, the device comprising a memory configured to store media data; and a processor implemented in circuitry and configured to process a box of file level information that describes a property of a track of a media file of media content including the media data, generate a descriptor for a manifest file of the media content, the descriptor corresponding to an adaptation set of the media content and including data representative of the box of the file level information, the media data of the track being included in the adaptation set, and send the manifest file including the descriptor to a client device.

Likewise, client device 40 represents an example of a device for retrieving media data including a memory configured to store media data; and a processor implemented in circuitry and configured to: process a descriptor of a manifest file of media content including the media data, the descriptor corresponding to an adaptation set of the media content and including data representative of a box of file level information that describes a property of a track of a media file of the media content including media data of the adaptation set, determine whether to retrieve the media data of the adaptation set according to the data representative of the file level information, and, in response to determining to retrieve the media data, send a request to retrieve the media data.

FIG. 2 is a block diagram illustrating an example set of components of retrieval unit 52 of FIG. 1 in greater detail. In this example, retrieval unit 52 includes eMBMS middleware unit 100, DASH client 110, and media application 112.

In this example, eMBMS middleware unit 100 further includes eMBMS reception unit 106, cache 104, and proxy server 102. In this example, eMBMS reception unit 106 is configured to receive data via eMBMS, e.g., according to File Delivery over Unidirectional Transport (FLUTE), described in T. Paila et al., “FLUTE—File Delivery over Unidirectional Transport,” Network Working Group, RFC 6726, November 2012, available at http://tools.ietf.org/html/rfc6726. That is, eMBMS reception unit 106 may receive files via broadcast from, e.g., server device 60, which may act as a BM-SC.

As eMBMS middleware unit 100 receives data for files, eMBMS middleware unit may store the received data in cache 104. Cache 104 may comprise a computer-readable storage medium, such as flash memory, a hard disk, RAM, or any other suitable storage medium.

Proxy server 102 may act as a server for DASH client 110. For example, proxy server 102 may provide a MPD file or other manifest file to DASH client 110. Proxy server 102 may advertise availability times for segments in the MPD file, as well as hyperlinks from which the segments can be retrieved. These hyperlinks may include a localhost address prefix corresponding to client device 40 (e.g., 127.0.0.1 for IPv4). In this manner, DASH client 110 may request segments from proxy server 102 using HTTP GET or partial GET requests. For example, for a segment available from link http://127.0.0.1/rep1/seg3, DASH client 110 may construct an HTTP GET request that includes a request for http://127.0.0.1/rep1/seg3, and submit the request to proxy server 102. Proxy server 102 may retrieve requested data from cache 104 and provide the data to DASH client 110 in response to such requests.

DASH client 110 may be configured according to any or all of the techniques of this disclosure as discussed above, alone or in any combination.

FIG. 3 is a conceptual diagram illustrating elements of example multimedia content 120. Multimedia content 120 may correspond to multimedia content 64 (FIG. 1 ), or another multimedia content stored in storage medium 62. In the example of FIG. 3 , multimedia content 120 includes media presentation description (MPD) 122 and a plurality of representations 124A-124N (representations 124). Representation 124A includes optional header data 126 and segments 128A-128N (segments 128), while representation 124N includes optional header data 130 and segments 132A-132N (segments 132). The letter N is used to designate the last movie fragment in each of representations 124 as a matter of convenience. In some examples, there may be different numbers of movie fragments between representations 124.

MPD 122 may comprise a data structure separate from representations 124. MPD 122 may correspond to manifest file 66 of FIG. 1 . Likewise, representations 124 may correspond to representations 68 of FIG. 2 . In general, MPD 122 may include data that generally describes characteristics of representations 124, such as coding and rendering characteristics, adaptation sets, a profile to which MPD 122 corresponds, text type information, camera angle information, rating information, trick mode information (e.g., information indicative of representations that include temporal sub-sequences), and/or information for retrieving remote periods (e.g., for targeted advertisement insertion into media content during playback).

Header data 126, when present, may describe characteristics of segments 128, e.g., temporal locations of random access points (RAPs, also referred to as stream access points (SAPs)), which of segments 128 includes random access points, byte offsets to random access points within segments 128, uniform resource locators (URLs) of segments 128, or other aspects of segments 128. Header data 130, when present, may describe similar characteristics for segments 132. Additionally or alternatively, such characteristics may be fully included within MPD 122.

Segments 128, 132 include one or more coded video samples, each of which may include frames or slices of video data. Each of the coded video samples of segments 128 may have similar characteristics, e.g., height, width, and bandwidth requirements. Such characteristics may be described by data of MPD 122, though such data is not illustrated in the example of FIG. 3 . MPD 122 may include characteristics as described by the 3GPP Specification, with the addition of any or all of the signaled information described in this disclosure.

Each of segments 128, 132 may be associated with a unique uniform resource locator (URL). Thus, each of segments 128, 132 may be independently retrievable using a streaming network protocol, such as DASH. In this manner, a destination device, such as client device 40, may use an HTTP GET request to retrieve segments 128 or 132. In some examples, client device 40 may use HTTP partial GET requests to retrieve specific byte ranges of segments 128 or 132.

MPD 122 may include data constructed according to any or all of the techniques of this disclosure, alone or in any combination.

FIG. 4 is a block diagram illustrating elements of an example video file 150, which may correspond to a segment of a representation, such as one of segments 114, 124 of FIG. 3 . Each of segments 128, 132 may include data that conforms substantially to the arrangement of data illustrated in the example of FIG. 4 . Video file 150 may be said to encapsulate a segment. As described above, video files in accordance with the ISO base media file format and extensions thereof store data in a series of objects, referred to as “boxes.” In the example of FIG. 4 , video file 150 includes file type (FTYP) box 152, movie (MOOV) box 154, segment index (sidx) boxes 162, movie fragment (MOOF) boxes 164, and movie fragment random access (MFRA) box 166. Although FIG. 4 represents an example of a video file, it should be understood that other media files may include other types of media data (e.g., audio data, timed text data, or the like) that is structured similarly to the data of video file 150, in accordance with the ISO base media file format and its extensions.

File type (FTYP) box 152 generally describes a file type for video file 150. File type box 152 may include data that identifies a specification that describes a best use for video file 150. File type box 152 may alternatively be placed before MOOV box 154, movie fragment boxes 164, and/or MFRA box 166.

In some examples, a Segment, such as video file 150, may include an MPD update box (not shown) before FTYP box 152. The MPD update box may include information indicating that an MPD corresponding to a representation including video file 150 is to be updated, along with information for updating the MPD. For example, the MPD update box may provide a URI or URL for a resource to be used to update the MPD. As another example, the MPD update box may include data for updating the MPD. In some examples, the MPD update box may immediately follow a segment type (STYP) box (not shown) of video file 150, where the STYP box may define a segment type for video file 150. FIG. 7 , discussed in greater detail below, provides additional information with respect to the MPD update box.

MOOV box 154, in the example of FIG. 4 , includes movie header (MVHD) box 156, track (TRAK) box 158, and one or more movie extends (MVEX) boxes 160. In general, MVHD box 156 may describe general characteristics of video file 150. For example, MVHD box 156 may include data that describes when video file 150 was originally created, when video file 150 was last modified, a timescale for video file 150, a duration of playback for video file 150, or other data that generally describes video file 150.

TRAK box 158 may include data for a track of video file 150. TRAK box 158 may include a track header (TKHD) box that describes characteristics of the track corresponding to TRAK box 158. In some examples, TRAK box 158 may include coded video pictures, while in other examples, the coded video pictures of the track may be included in movie fragments 164, which may be referenced by data of TRAK box 158 and/or sidx boxes 162. Moreover, in accordance with the techniques of this disclosure, a manifest file (such as an MPD) may include data representing data of TRAK box 158, albeit separately from video file 150. In this manner, client device 40 (FIG. 1 ) may avoid retrieving video file 150 initially and determine whether to retrieve video file 150 (or a portion thereof, such as a particular track of video file 150) using the data of the manifest file representative of TRAK box 158.

In some examples, video file 150 may include more than one track. Accordingly, MOOV box 154 may include a number of TRAK boxes equal to the number of tracks in video file 150. TRAK box 158 may describe characteristics of a corresponding track of video file 150. For example, TRAK box 158 may describe temporal and/or spatial information for the corresponding track. A TRAK box similar to TRAK box 158 of MOOV box 154 may describe characteristics of a parameter set track, when encapsulation unit 30 (FIG. 3 ) includes a parameter set track in a video file, such as video file 150. Encapsulation unit 30 may signal the presence of sequence level SEI messages in the parameter set track within the TRAK box describing the parameter set track.

MVEX boxes 160 may describe characteristics of corresponding movie fragments 164, e.g., to signal that video file 150 includes movie fragments 164, in addition to video data included within MOOV box 154, if any. In the context of streaming video data, coded video pictures may be included in movie fragments 164 rather than in MOOV box 154. Accordingly, all coded video samples may be included in movie fragments 164, rather than in MOOV box 154.

MOOV box 154 may include a number of MVEX boxes 160 equal to the number of movie fragments 164 in video file 150. Each of MVEX boxes 160 may describe characteristics of a corresponding one of movie fragments 164. For example, each MVEX box may include a movie extends header box (MEHD) box that describes a temporal duration for the corresponding one of movie fragments 164.

As noted above, encapsulation unit 30 may store a sequence data set in a video sample that does not include actual coded video data. A video sample may generally correspond to an access unit, which is a representation of a coded picture at a specific time instance. In the context of AVC, the coded picture includes one or more VCL NAL units which contains the information to construct all the pixels of the access unit and other associated non-VCL NAL units, such as SEI messages. Accordingly, encapsulation unit 30 may include a sequence data set, which may include sequence level SEI messages, in one of movie fragments 164. Encapsulation unit 30 may further signal the presence of a sequence data set and/or sequence level SEI messages as being present in one of movie fragments 164 within the one of MVEX boxes 160 corresponding to the one of movie fragments 164.

SIDX boxes 162 are optional elements of video file 150. That is, video files conforming to the 3GPP file format, or other such file formats, do not necessarily include SIDX boxes 162. In accordance with the example of the 3GPP file format, a SIDX box may be used to identify a sub-segment of a segment (e.g., a segment contained within video file 150). The 3GPP file format defines a sub-segment as “a self-contained set of one or more consecutive movie fragment boxes with corresponding Media Data box(es) and a Media Data Box containing data referenced by a Movie Fragment Box must follow that Movie Fragment box and precede the next Movie Fragment box containing information about the same track.” The 3GPP file format also indicates that a SIDX box “contains a sequence of references to subsegments of the (sub)segment documented by the box. The referenced subsegments are contiguous in presentation time. Similarly, the bytes referred to by a Segment Index box are always contiguous within the segment. The referenced size gives the count of the number of bytes in the material referenced.”

SIDX boxes 162 generally provide information representative of one or more sub-segments of a segment included in video file 150. For instance, such information may include playback times at which sub-segments begin and/or end, byte offsets for the sub-segments, whether the sub-segments include (e.g., start with) a stream access point (SAP), a type for the SAP (e.g., whether the SAP is an instantaneous decoder refresh (IDR) picture, a clean random access (CRA) picture, a broken link access (BLA) picture, or the like), a position of the SAP (in terms of playback time and/or byte offset) in the sub-segment, and the like.

Movie fragments 164 may include one or more coded video pictures. In some examples, movie fragments 164 may include one or more groups of pictures (GOPs), each of which may include a number of coded video pictures, e.g., frames or pictures. In addition, as described above, movie fragments 164 may include sequence data sets in some examples. Each of movie fragments 164 may include a movie fragment header box (MFHD, not shown in FIG. 4 ). The MFHD box may describe characteristics of the corresponding movie fragment, such as a sequence number for the movie fragment. Movie fragments 164 may be included in order of sequence number in video file 150.

MFRA box 166 may describe random access points within movie fragments 164 of video file 150. This may assist with performing trick modes, such as performing seeks to particular temporal locations (i.e., playback times) within a segment encapsulated by video file 150. MFRA box 166 is generally optional and need not be included in video files, in some examples. Likewise, a client device, such as client device 40, does not necessarily need to reference MFRA box 166 to correctly decode and display video data of video file 150. MFRA box 166 may include a number of track fragment random access (TFRA) boxes (not shown) equal to the number of tracks of video file 150, or in some examples, equal to the number of media tracks (e.g., non-hint tracks) of video file 150.

In some examples, movie fragments 164 may include one or more stream access points (SAPs), such as IDR pictures. Likewise, MFRA box 166 may provide indications of locations within video file 150 of the SAPs. Accordingly, a temporal sub-sequence of video file 150 may be formed from SAPs of video file 150. The temporal sub-sequence may also include other pictures, such as P-frames and/or B-frames that depend from SAPs. Frames and/or slices of the temporal sub-sequence may be arranged within the segments such that frames/slices of the temporal sub-sequence that depend on other frames/slices of the sub-sequence can be properly decoded. For example, in the hierarchical arrangement of data, data used for prediction for other data may also be included in the temporal sub-sequence.

Video file 150 may include data constructed according to any or all of the techniques of this disclosure, alone or in any combination.

FIG. 5 is a conceptual diagram illustrating an example content model 180 for DASH multitrack. In the DASH Technologies under Consideration (TuC), the model on content annotation and decisions has been updated to address the selection of content. In order to support the content author in providing content in a consistent manner, FIG. 5 provides a conceptual content model for DASH content in one Period of an MPD. The content may be described by an Asset Identifier as a whole and may contain different media types, video, audio, subtitle and application types.

In particular, content model 180 includes content 182, described as a whole by asset description 204. Content 182 may include multiple, various media types 206, such as media type video 184, media type audio 186, media type subtitle 188 (also referred to as timed text), and/or media type application 190. The various types of media content may be provided in sets of media types, such as media type content main 192, media type content alternative (alt) 1 194, and media type content alt 2 196. A media application may select one of these sets of media types, such that the collection of sets of media types may be referred to as application-based selection media 208. These sets may further correspond to target version adaptation sets 200A-200C (target version adaptation sets 200), which client device 40 may select through an automated system-based selection process 210. Target version adaptation sets 200 may each include respective encoded representations 202A-202C of various bitrates to provide for dynamic switching 212, e.g., as available bandwidth increases or decreases.

Within each of multiple media types 206, the content author may want to offer different alternative content that are time-aligned (e.g., media type content main, media type content alt 1 194, and media type content alt 2 196), but each alternative represents different content. Automatic selection of the alternative content is not expected to be done by the DASH client as the DASH client would not have sufficient information to make such decisions. However, the selection is expected to be done by communication with an application or the user, typically using a user interface appropriate for selection.

In the absence of this external communication, or at startup, the DASH client still needs to playback content, and therefore benefits from information indicative of default content. Such signalling should be provided by the content author. Such default content may be referred to as main content (e.g., media type content main 192), whereas any content that is not main may be referred to as alternative (e.g., media type content alt 1 194, media type content alt 2 196). There may be multiple alternatives which may need to be distinguished. This disclosure defines main and alternative content. Examples for such are synchronized camera views of one master content. The main camera view is provided as main content, all other views as alternative content.

Furthermore, it may be that content of different media types are linked by the content author, to express that two contents of different media types are preferably played together. This disclosure defines associated contents for this purpose. As an example, there may be a main commentator associated with the main camera view, but for a different camera view, a different associated commentary is provided.

In addition to semantical content level differentiation, each alternative content may be prepared with different target versions, based on content preparation properties (downmix, subsampling, translation, suitable for trick mode, etc.), client preferences (decoding or rendering preferences, e.g. codec), client capabilities (DASH profile support, decoding capabilities, rendering capabilities) or user preferences (accessibility, language, etc.). In simple AV playout and in the absence of guidance from an application, a content author expects that the DASH client selects at most one target version for each Group (e.g., one of target version adaptation sets 200), taking into account its capabilities and preferences and the capabilities and preferences of the media subsystem. However, an application may obviously select multiple Groups and playout different video Adaptation Sets to support for example picture-in-picture, multi-angle and so on.

In addition, the content author may also provide priorities for target versions, if the receivers support selection of content according to multiple priorities. Typical examples are that the content is prepared for H.264/AVC and H.265/HEVC capable receivers, and the content author prefers the selection of the H.265/HEVC version as its distribution is more efficient. A device supporting both decoders may then choose the one with higher priority signalled by the content author. In a similar version, the same content may be provided in different languages. In this case, it can still be expected that the language can be automatically selected by the client, so it is assigned to a target version. Again, a content author may express priorities on languages, for example preferring the native language over a dubbed one. Languages may be considered as alternative content as well, but as long as automatic selection can be provided, it may be considered as different target versions. Hence for each content of one media type, different target versions may exist and the annotation of the content expressed that it is expected that automated selection can be done. Each target version is preferably accumulated in one Adaptation Set, with exceptions such as scalable codecs.

Finally, in the content model, each of the target version typically has multiple encoded representations 202 that are prepared to enable dynamic switching. This aspect is outside the scope of this section as switching by the client is expected to be done independent of the media type as well as the target version, primarily using the bandwidth and possibly abstract quality information. However, the signalling on the target versions may provide information on how to distribute the available bitrate across different media types.

Based on this content model and the available elements, attributes and descriptors in DASH, the TuC of DASH provides requirements and recommendations for Adaptation Set Signalling to address main and alternative content, associated content as well as different target versions. Based on the signalling, a client decision model is developed that may serve a content provider as a reference client to test if the annotation provided in the MPD provides the proper results.

FIG. 6 is a conceptual diagram illustrating an example client model 220. In particular, client model 220 includes DASH client 232, media application 238, file format processing unit 240, media decoder 242, media renderer 244, and output device 246. DASH client 232 and media application 238 may generally correspond to retrieval unit 52 of FIG. 1 , file format processing unit 240 may correspond to decapsulation unit 50 of FIG. 1 , and media decoder 242 may correspond to either or both of audio decoder 46 and video decoder 48, and media renderer 244 and output device 246 may correspond to either or both of audio output 42 and video output 44 of FIG. 1 .

In this example, each of file formats 222A-222C (file formats 222) includes respective representations 224A, 224B, 226A, 226B, 228A, 228B, described by MPD 230 (an example of a manifest file). MPD 230 includes data according to the techniques of this disclosure describing properties of tracks of media files formatted according to one of file formats 222. Thus, DASH client 232 initially retrieves MPD 230. DASH client 232 receives requested media data (e.g., user preferences, priorities, device capabilities, or the like) from media application 238, in this example. DASH client 232 processes the data of MPD 230 to determine properties of tracks of file formats 222, to cause selection unit 234 to select an appropriate one of file formats 222 for, e.g., file format processing unit 240 and conforming to user preferences, priorities, and the like. Download & switching unit 236 of DASH client 232 then retrieves media data of one of representations 224A, 224B, 226A, 226B, 228A, or 228B, according to which of file formats 222 was selected and an available amount of network bandwidth. DASH client 230 provides the retrieved media data to file format processing unit 240, which decapsulates the media data and provides the media data to media application 238. Media application 238, in turn, provides the media data to media decoder 242, which decodes the media data and passes the decoded media data to media renderer 244. Media renderer 244, in turn, renders the media data and provides the rendered media data to output device 246 for output (e.g., audio or video output).

With reference to the terms “main content,” “associated content,” and “target versions” above, DASH client 232 may operate selection unit 234 that is configured to perform selection according to communication with media application 238 in FIG. 6 . This selection is based on information in MPD 230, assigned to each Adaptation Set (or Preselection, if DASH Amd. 4 is in place) of file formats 222. A content preparation device, such as content preparation device 20 of FIG. 1 , adds sufficient additional metadata to MPD 230 in order to enable the selection, in accordance with the techniques of this disclosure. Typically, DASH client 232 extracts this information, which is aligned with information that is also present in the ISO BMFF track, primarily because of the track metadata provide sufficient information to describe the track.

In even another option, file formats 222 (and potentially also application formats, such as OMAF) define sufficient information for description of the tracks for selection. The generic file format processor typically also communicates with the application in order to properly make use of the track and to possibly render the track.

The information in DASH and ISO Base Media File Format may be identical in expressing information for media application 238 for their selection. It may be confusing if the metadata in the file format is not aligned with the information in the file format.

Not necessarily all information needs to be expressed on DASH level for the purpose for selection, but sufficient information may be expressed in order to provide media application 238 and selection unit 234 the ability to properly differentiate and select between file formats 222.

Conventionally, this is solved primarily by the file format defining specific metadata information, and on DASH level, some descriptors are defined that more less may match. However, this requires a completely new definition in DASH and unnecessarily may delay work, as the descriptors need to be done afterwards. The approach is also error-prone and typically not complete and comprehensive. It would be much more suitable that any metadata definition in ISO BMFF formats is automatically exposed to DASH level and the DASH client is aware that the information included in the DASH “descriptor” is aligned with file format definition. This also allows the same information to be interpreted in the same way by the application, independent of the source.

Conventionally, a descriptor is defined for each and every type of file format information that needs to be exposed to the DASH MPD, resulting in many complex descriptor definitions, and mismatches between the signaling in the MPD and in file format boxes can easy occur.

Referring back to FIG. 1 , content preparation device 20, server device 60, and client device 40 may be configured according to the following basic design, per the techniques of this disclosure:

-   -   1) For any file level information that describes the property of         a track, the information can be exposed at the DASH level by an         automatic conversion of the 4-character code (4CC), the version         number, and the content of the box.     -   2) Either all information in a box is provided, or a part of all         information that is relevant is provided.     -   3) The information can be used as a regular descriptor in DASH         that can be used for the selection of Adaptation Sets and         Preselections.

The mechanisms above may be used to replace all the descriptors, namely PF, RWPK, CC, and RWQR descriptors, defined in clause 8.2 of the OMAF draft text in m40849, or may be used in addition to these descriptors.

The exposition of such information may follow different design choices. Example design choices are described below:

Example option 0: add movie header. This is the simplest version and only provides the Movie Header in the MPD. This obviously contains relevant information, but results in detailed parsing, and key information may be lost.

Example option 1: generate automated descriptor. In this example, an automated descriptor is generated that can be used with the DASH Essential and Supplemental property descriptor. In this case, the regular descriptor mode in DASH can be used. The descriptor may be generated by a prefix such as urn:mpeg:isobmff-dash:<4cc>:<version>, and the value may be the content of the data in the box. One advantage of this approach is that it is simple, but the value field may be large, and non-essential data may possibly be added. This example also allows this method to be applied to existing features.

Example option 2: generate extensions namespace and XML. In this example, when defining a new box, an element is also created that can used as an extension namespace in the MPD. The element is generated consciously, such that all relevant parameters of the box can be documented in the XML descriptor as well, for example, by the use of elements and attributes, mandatory and optional parameters, proper data types, and the like. One advantage of this approach is that it is more powerful and readable, but the diligence of the design is important, and this does not apply for existing data. In order to indicate whether the processing of the metadata is supplemental or essential, a generic descriptor may be added that refers to the 4CC.

Example option 3: Mix of example options 1 and 2. In this example, the descriptor is generated automatically, but instead of using a single value field, an automated syntax for expressing all data in the box is provided. The syntax may, for example, be an automatically generated XML or an automatically generated Augmented Backus-Naur Form (ABNF). Reuse of existing functionalities is encouraged.

In one example, a projected omnidirectional video box may be added. Various options are described below for adding data to an Adaptation Set element.

Example Option 1: Add Movie Header

-   -   @movieHeader=“Xxxuxox”

Example Option 2: Add Descriptor

<EssentialDescriptor    schemeUdURI=“urn:mpeg:isobmff-dash:povd:0”    value=“Xxxuxox” />

Example Option 3: Extension Namespace

<EssentialDescriptor    schemeUdURI=urn:mpeg:isobmff-dash:processing    value=“povd”/> <isobmff:povd       projectionType=0/> />

Example Option 4: Automated Generation

<EssentialDescriptor    schemeUdURI=urn:mpeg:isobmff-dash:processing    value=“povd”/> <isobmff:povd    <prfr       projection_type=0/> />

FIG. 7 is a flowchart illustrating an example method for generating media data and for retrieving media data in accordance with the techniques of this disclosure. The method of FIG. 7 is explained with respect to content preparation device 20 and client device 40 of FIG. 1 , although it should be understood that other devices may be configured to perform this or a similar method. For example, server device 60 may be configured to perform some or all of the elements attributed to content preparation device 20.

Initially, content preparation device 20 obtains a media file (300). The media file may include audio data, video data, timed text data, or the like. For example, the media file may correspond to media content according to the model shown in FIG. 5 . The media file may conform to ISO BMFF, e.g., as shown in FIG. 4 . It is assumed that the media file includes one or more track boxes, such as TRAK box 158, which describe properties of respective tracks of the media file. Thus, content preparation device 20 determines the boxes of the media file describing the tracks (302).

Content preparation device 20 further generates descriptors including data for the boxes (304), in this example. For example, the descriptor may be a single element or multiple elements of an extension namespace, as discussed above. The data for the box may include, for example, a four character code (4CC) of the box, a version of the box, and some or all of the content of the box. For example, the generated descriptors may correspond to any or all of example options 1-4 discussed above.

Content preparation device 20 may then add the descriptors to a manifest file (306), such as a DASH MPD, for the media content. Content preparation device 20 then sends the manifest file to client device 40 (308). Client device 40 receives the manifest file (310) and processes the descriptors of the manifest file (312) to select one or more adaptation sets using the descriptors (314). For example, as discussed above, client device 40 may select the adaptation sets according to user preferences, priorities, capabilities of client device 40 (e.g., decoding and rendering capabilities, file format processing capabilities, or the like), or other such selection criteria.

Ultimately, client device 40 may send a request for media data of a selected adaptation set (316) to content preparation device 20 (or server device 60). In particular, client device 40 may determine one of the representations of the adaptation set from which to retrieve media data of a track corresponding to the selected adaptation set, e.g., based on an available amount of network bandwidth and a bitrate of the representation. Content preparation device 20 (or server device 60) may receive the request (318) and send the requested media data to client device 40 (320). Ultimately, client device 40 may receive the media data (322) and send the media data to a media decoder (324) to be decoded, and ultimately rendered and presented.

In this manner, the method of FIG. 7 represents an example of a method of generating media data including processing a box of file level information that describes a property of a track of a media file of media content including media data, generating a descriptor for a manifest file of the media content, the descriptor corresponding to an adaptation set of the media content and including data representative of the box of the file level information, the media data of the track being included in the adaptation set, and sending the manifest file including the descriptor to a client device.

The method of FIG. 7 also represents an example of a method of retrieving media data including processing a descriptor of a manifest file of media content, the descriptor corresponding to an adaptation set of the media content and including data representative of a box of file level information that describes a property of a track of a media file of the media content including media data of the adaptation set, determining whether to retrieve the media data of the adaptation set according to the data representative of the file level information, and, in response to determining to retrieve the media data, sending a request to retrieve the media data.

In one or more examples, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium and executed by a hardware-based processing unit. Computer-readable media may include computer-readable storage media, which corresponds to a tangible medium such as data storage media, or communication media including any medium that facilitates transfer of a computer program from one place to another, e.g., according to a communication protocol. In this manner, computer-readable media generally may correspond to (1) tangible computer-readable storage media which is non-transitory or (2) a communication medium such as a signal or carrier wave. Data storage media may be any available media that can be accessed by one or more computers or one or more processors to retrieve instructions, code, and/or data structures for implementation of the techniques described in this disclosure. A computer program product may include a computer-readable medium.

By way of example, and not limitation, such computer-readable storage media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage, or other magnetic storage devices, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer. Also, any connection is properly termed a computer-readable medium. For example, if instructions are transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. It should be understood, however, that computer-readable storage media and data storage media do not include connections, carrier waves, signals, or other transitory media, but are instead directed to non-transitory, tangible storage media. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.

Instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general purpose microprocessors, application specific integrated circuits (ASICs), field programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuitry. Accordingly, the term “processor,” as used herein may refer to any of the foregoing structure or any other structure suitable for implementation of the techniques described herein. In addition, in some aspects, the functionality described herein may be provided within dedicated hardware and/or software modules configured for encoding and decoding, or incorporated in a combined codec. Also, the techniques could be fully implemented in one or more circuits or logic elements.

The techniques of this disclosure may be implemented in a wide variety of devices or apparatuses, including a wireless handset, an integrated circuit (IC) or a set of ICs (e.g., a chip set). Various components, modules, or units are described in this disclosure to emphasize functional aspects of devices configured to perform the disclosed techniques, but do not necessarily require realization by different hardware units. Rather, as described above, various units may be combined in a codec hardware unit or provided by a collection of interoperative hardware units, including one or more processors as described above, in conjunction with suitable software and/or firmware.

Various examples have been described. These and other examples are within the scope of the following claims. 

What is claimed is:
 1. A method of retrieving media data, the method comprising: retrieving a manifest file of media content, the manifest file including a first descriptor and a second descriptor, the first descriptor being formatted according to extensible markup language (XML) or Augmented Backus-Naur Form (ABNF) and forming part of a first adaptation set element of the manifest file, the first descriptor including data representative of a first track (TRAK) box of file level information that describes a property of a first track of a first media file of the media content including media data of the first adaptation set, the second descriptor being formatted according to XML or ABNF and forming part of a second adaptation set element of the manifest file, the second descriptor including data representative of a second TRAK box of the file level information that describes the property of a second track of a second media file, and wherein retrieving the manifest file comprises retrieving the manifest file prior to retrieving any media data described by the manifest file; processing the first descriptor of the manifest file to determine the data representative of the first TRAK box of the file level information that describes the property of the first track of the first media file and the second descriptor of the manifest file to determine the data representative of the second TRAK box of the file level information that describes the property of the second track of the second media file; determining whether to retrieve either the first track of the first media file or the second track of the second media file according to the first descriptor including the data representative of the first TRAK box of the file level information and the second descriptor including the data representative of the second TRAK box of the file level information; sending a request to retrieve either the first track of the first media file or the second track of the second media file according to the determination; and in response to the request, receiving either data for the first track of the media file including the first TRAK box formatted according to ISO Base Media File Format (ISO BMFF) or the second track of the media file including the second TRAK box formatted according to ISO BMFF.
 2. The method of claim 1, wherein the data representative of the first TRAK box of the file level information comprises data representing at least a first four character code of the first TRAK box, a first version of the first TRAK box, and first content of the first TRAK box.
 3. The method of claim 1, wherein processing the first descriptor comprises processing a first prefix comprising “urn:mpeg:isobmff-dash:<4cc>:<version>” preceding a first value, wherein <4cc> of the first prefix comprises data representing a first four character code of the first TRAK box, <version> of the first prefix comprises data representing a first version of the first TRAK box, and the first value comprises data representing first content of the first TRAK box.
 4. The method of claim 1, wherein the first descriptor is a first single value field of the manifest file.
 5. The method of claim 1, wherein the first descriptor comprises one of an essential descriptor or a supplemental descriptor.
 6. The method of claim 1, wherein processing the first descriptor comprises processing an extension namespace identifier of the first descriptor, the method further comprising processing one or more elements of the manifest file for the extension namespace, the one or more elements including data representing content of the first TRAK box.
 7. The method of claim 6, wherein processing the one or more elements comprises processing one or more attributes, mandatory parameters, optional parameters, or values having proper data types.
 8. The method of claim 6, wherein processing the first descriptor comprises processing a prefix comprising “urn:mpeg:isobmff-dash:processing” preceding a value, the value defining the extension namespace identifier.
 9. The method of claim 6, wherein the one or more elements are expressed in extensible markup language (XML) format.
 10. The method of claim 6, wherein the one or more elements are expressed in Augmented Backus-Naur Form (ABNF) format.
 11. The method of claim 6, wherein processing the first descriptor comprises processing data of the first descriptor corresponding to a four character code of the first TRAK box.
 12. The method of claim 1, wherein the manifest file comprises a Dynamic Adaptive Streaming over HTTP (DASH) Media Presentation Description (MPD).
 13. A device for retrieving media data, the device comprising: a memory configured to store media data; and a processor implemented in circuitry and configured to: retrieve a manifest file of media content, the manifest file including a first descriptor and a second descriptor, the first descriptor being formatted according to extensible markup language (XML) or Augmented Backus-Naur Form (ABNF) and forming part of a first adaptation set element of the manifest file, the first descriptor including data representative of a first track (TRAK) box of file level information that describes a property of a first track of a first media file of the media content including media data of the first adaptation set, the second descriptor being formatted according to XML or ABNF and forming part of a second adaptation set element of the manifest file, the second descriptor including data representative of a second TRAK box of the file level information that describes the property of a second track of a second media file, and wherein retrieving the manifest file comprises retrieving the manifest file prior to retrieving any media data described by the manifest file; process the first descriptor of the manifest file to determine the data representative of the first TRAK box of the file level information that describes the property of the first track of the first media file and the second descriptor of the manifest file to determine the data representative of the second TRAK box of the file level information that describes the property of the second track of the second media file; determine whether to retrieve either the first track of the first media file or the second track of the second media file according to the first descriptor including the data representative of the first TRAK box of the file level information and the second descriptor including the data representative of the second TRAK box of the file level information; send a request to retrieve either the first track of the first media file or the second track of the second media file according to the determination; and in response to the request, receive either data for the first track of the media file including the first TRAK box formatted according to ISO Base Media File Format (ISO BMFF) or the second track of the media file including the second TRAK box formatted according to ISO BMFF.
 14. The device of claim 13, wherein the data representative of the first TRAK box of the file level information comprises data representing at least a first four character code of the first TRAK box, a first version of the first TRAK box, and first content of the first TRAK box.
 15. The device of claim 13, wherein the processor is configured to process a first prefix comprising “urn:mpeg:isobmff-dash:<4cc>:<version>” preceding a first value, wherein <4cc> of the first prefix comprises data representing a first four character code of the first TRAK box, <version> comprises data representing a first version of the first TRAK box, and the first value comprises data representing first content of the first TRAK box.
 16. The device of claim 13, wherein the first descriptor is a first single value field of the manifest file.
 17. The device of claim 13, wherein the processor is configured to process an extension namespace identifier of the first descriptor and one or more elements of the manifest file for the extension namespace, the one or more elements including data representing content of the first TRAK box.
 18. The device of claim 17, wherein the processor is configured to process a prefix comprising “urn:mpeg:isobmff-dash:processing” preceding a value, the value defining the extension namespace identifier.
 19. The device of claim 17, wherein the one or more elements are expressed in one of extensible markup language (XML) format or Augmented Backus-Naur Form (ABNF) format.
 20. The device of claim 17, wherein the processor is configured to process data of the first descriptor corresponding to a first four character code of the first TRAK box.
 21. The device of claim 13, wherein the manifest file comprises a Dynamic Adaptive Streaming over HTTP (DASH) Media Presentation Description (MPD).
 22. A non-transitory computer-readable storage medium having stored thereon instructions that, when executed, cause a processor to: retrieve a manifest file of media content, the manifest file including a first descriptor and a second descriptor, the first descriptor being formatted according to extensible markup language (XML) or Augmented Backus-Naur Form (ABNF) and forming part of a first adaptation set element of the manifest file, the first descriptor including data representative of a first track (TRAK) box of file level information that describes a property of a first track of a first media file of the media content including media data of the first adaptation set, the second descriptor being formatted according to XML, or ABNF and forming part of a second adaptation set element of the manifest file, the second descriptor including data representative of a second TRAK box of the file level information that describes the property of a second track of a second media file, and wherein retrieving the manifest file comprises retrieving the manifest file prior to retrieving any media data described by the manifest file; process the first descriptor of the manifest file to determine the data representative of the first TRAK box of the file level information that describes the property of the first track of the first media file and the second descriptor of the manifest file to determine the data representative of the second TRAK box of the file level information that describes the property of the second track of the second media file; determine whether to retrieve either the first track of the first media file or the second track of the second media file according to the first descriptor including the data representative of the first TRAK box of the file level information and the second descriptor including the data representative of the second TRAK box of the file level information; send a request to retrieve either the first track of the first media file or the second track of the second media file according to the determination; and in response to the request, receive either data for the first track of the media file including the first TRAK box formatted according to ISO Base Media File Format (ISO BMFF) or the second track of the media file including the second TRAK box formatted according to ISO BMFF.
 23. The non-transitory computer-readable storage medium of claim 22, wherein the instructions that cause the processor to process the first descriptor comprise instructions that cause the processor to process an extension namespace identifier of the first descriptor, further comprising instructions that cause the processor to process one or more elements of the manifest file for the extension namespace, the one or more elements including data representing content of the first TRAK box.
 24. The non-transitory computer-readable storage medium of claim 23, wherein the instructions that cause the processor to process the descriptor comprise instructions that cause the processor to process data of the descriptor corresponding to a four character code of the box.
 25. A method of generating media data, the method comprising: processing a first track (TRAK) box of file level information that describes a first property of a first track of a first media file of media content including first media data; determining first data representative of the first TRAK box of the file level information; generating a first descriptor for a manifest file of the media content, the first descriptor corresponding to a first adaptation set of the media content, wherein generating the first descriptor comprises adding the first data representative of the first TRAK box of the file level information to the first descriptor, the first media data of the first track being included in the first adaptation set; adding the first descriptor to a first adaptation set element of the manifest file, the first adaptation set element corresponding to the first adaptation set; processing a second TRAK box of file level information that describes a second property of a second track of a second media file of the media content including second media data; determining second data representative of the second TRAK box of the file level information; generating a second descriptor for the manifest file of the media content, the second descriptor corresponding to a second adaptation set of the media content, wherein generating the second descriptor comprises adding the second data representative of the second TRAK box of the file level information to the second descriptor, the second media data of the second track being included in the second adaptation set; adding the second descriptor to a second adaptation set element of the manifest file, the second adaptation set element corresponding to the second adaptation set; and sending the manifest file including the first descriptor and the second descriptor to a client device.
 26. The method of claim 25, wherein generating the first descriptor comprises generating the first descriptor to include data representing at least a first four character code of the first TRAK box, a first version of the first TRAK box, and first content of the first TRAK box.
 27. The method of claim 25, wherein generating the first descriptor comprises generating a first prefix comprising “urn:mpeg:isobmff-dash:<4cc>:<version>” preceding a first value, and generating the first value, wherein <4cc> comprises first data representing a first four character code of the box, <version> comprises first data representing a first version of the first TRAK box, and the first value comprises first data representing content of the first TRAK box.
 28. The method of claim 25, wherein the first descriptor is a single value field of the manifest file.
 29. The method of claim 25, wherein the first descriptor comprises one of an essential descriptor or a supplemental descriptor.
 30. The method of claim 25, wherein generating the first descriptor comprises generating an extension namespace identifier of the first descriptor, the method further comprising generating one or more elements of the manifest file for the extension namespace, the one or more elements including data representing content of the first TRAK box.
 31. The method of claim 30, wherein generating the one or more elements comprises generating one or more attributes, mandatory parameters, optional parameters, or values having proper data types.
 32. The method of claim 30, wherein generating the first descriptor comprises generating a prefix comprising “urn:mpeg:isobmff-dash:processing” preceding a value, and generating the value, the value defining the extension namespace identifier.
 33. The method of claim 30, wherein generating the one or more elements comprises generating the elements in extensible markup language (XML) format.
 34. The method of claim 30, wherein generating the one or more elements comprises generating the elements in Augmented Backus-Naur Form (ABNF) format.
 35. The method of claim 30, wherein generating the first descriptor comprises generating data of the first descriptor to represent a four character code of the first TRAK box.
 36. The method of claim 25, wherein the manifest file comprises a Dynamic Adaptive Streaming over HTTP (DASH) Media Presentation Description (MPD).
 37. A device for generating media data, the device comprising: a memory configured to store media data; and a processor implemented in circuitry and configured to: process a first track (TRAK) box of file level information that describes a first property of a first track of a first media file of media content including first media data; determine first data representative of the first TRAK box of the file level information; generate a first descriptor for a manifest file of the media content, the first descriptor corresponding to a first adaptation set of the media content, wherein generating the first descriptor comprises adding the first data representative of the first TRAK box of the file level information to the first descriptor, the first media data of the first track being included in the first adaptation set; add the first descriptor to a first adaptation set element of the manifest file, the first adaptation set element corresponding to the first adaptation set; process a second TRAK box of file level information that describes a second property of a second track of a second media file of the media content including second media data; determine second data representative of the second TRAK box of the file level information; generate a second descriptor for the manifest file of the media content, the second descriptor corresponding to a second adaptation set of the media content, wherein generating the second descriptor comprises adding the second data representative of the second TRAK box of the file level information to the second descriptor, the second media data of the second track being included in the second adaptation set; add the second descriptor to a second adaptation set element of the manifest file, the second adaptation set element corresponding to the second adaptation set; and send the manifest file including the first descriptor and the second descriptor to a client device.
 38. The device of claim 37, wherein the processor is configured to generate the first descriptor to include data representing at least a first four character code of the first TRAK box, a first version of the first TRAK box, and first content of the first TRAK box.
 39. The device of claim 37, wherein the processor is configured to generate a first prefix comprising “urn:mpeg:isobmff-dash:<4cc>:<version>” preceding a first value, and generate the first value, wherein <4cc> comprises data representing a first four character code of the first TRAK box, <version> comprises data representing a first version of the first TRAK box, and the first value comprises data representing first content of the first TRAK box.
 40. The device of claim 37, wherein the first descriptor is a single value field of the manifest file.
 41. The device of claim 37, wherein generating the first descriptor comprises generating an extension namespace identifier of the first descriptor, the method further comprising generating one or more elements of the manifest file for the extension namespace, the one or more elements including data representing content of the first TRAK box.
 42. The device of claim 41, wherein the processor is configured to generate a prefix comprising “urn:mpeg:isobmff-dash:processing” preceding a value, and generating the value, the value defining the extension namespace identifier.
 43. The device of claim 41, wherein the processor is configured to generate the elements in one of extensible markup language (XML) format or Augmented Backus-Naur Form (ABNF) format.
 44. The device of claim 41, wherein the processor is configured to generate data of the first descriptor to represent a first four character code of the first TRAK box.
 45. The device of claim 37, wherein the manifest file comprises a Dynamic Adaptive Streaming over HTTP (DASH) Media Presentation Description (MPD).
 46. A non-transitory computer-readable storage medium having stored thereon instructions that, when executed, cause a processor to: process a first track (TRAK) box of file level information that describes a first property of a first track of a first media file of media content including first media data; determine first data representative of the first TRAK box of the file level information; generate a first descriptor for a manifest file of the media content, the first descriptor corresponding to a first adaptation set of the media content, wherein generating the first descriptor comprises adding the first data representative of the first TRAK box of the file level information to the first descriptor, the first media data of the first track being included in the first adaptation set; add the first descriptor to a first adaptation set element of the manifest file, the first adaptation set element corresponding to the first adaptation set; processing a second TRAK box of file level information that describes a second property of a second track of a second media file of the media content including second media data; determine second data representative of the second TRAK box of the file level information; generate a second descriptor for the manifest file of the media content, the second descriptor corresponding to a second adaptation set of the media content, wherein generating the second descriptor comprises adding the second data representative of the second TRAK box of the file level information to the second descriptor, the second media data of the second track being included in the second adaptation set; add the second descriptor to a second adaptation set element of the manifest file, the second adaptation set element corresponding to the second adaptation set; and send the manifest file including the first descriptor and the second descriptor to a client device.
 47. The non-transitory computer-readable storage medium of claim 46, wherein the instructions that cause the processor to generate the first descriptor comprise instructions that cause the processor to generate an extension namespace identifier of the first descriptor, further comprising instructions that cause the processor to generate one or more elements of the manifest file for the extension namespace, the one or more elements including data representing content of the first TRAK box.
 48. The non-transitory computer-readable storage medium of claim 47, wherein the instructions that cause the processor to generate the first descriptor comprise instructions that cause the processor to generate data of the first descriptor corresponding to a four character code of the first TRAK box. 